Simulation study of beam-beam effects

The Beijing Electron-Positron Collider (BEPC) will be upgraded to BEPCII, and the luminosity will be about 100 times higher. We developed a three-dimensional strong-strong PIC code to study the beam-beam effects in BEPCII. The transportation through the arc is the same as that in Hirata’s weak-strong code. The beam-beam force is computed directly by solving the Poisson equation using the Fourier analysis and cyclic reduction method, and the boundary potential is computed by circular convolution. The finite bunch length effect is included by longitudinal slices. An interpolation scheme is used to reduce the required slice number in simulations. The standard message passing interface is used to parallelize the code. The computing time increases linearly with (n+1), where n is the slice number. The calculated luminosity of BEPCII at the design working point is ∼50% of the design value. The best area in the tune space is near (0.505,0.57) according to the survey, where the luminosity is ∼80% of the design.